This invention relates to an opening roller for open-end spinning machines comprising a cylindrical roller body and a sawtooth wire wound helically onto the outer surface thereof which has a base region widened in relation to the teeth and which is wound under tension onto the outer surface and fixed at its ends to the roller body, the base regions of adjacent turns of the sawtooth wire being separated by a gap from one another.
One known opening roller of this type (German Auslegeschrift No. 2,364,544) uses standard commercial sawtooth wires of the kind used for example in cards for carding fibrous material. Standardised sawtooth wires such as these are obtainable with base regions between 1.3 and 1.5 mm in height.
It has been found that opening rollers such as these give a yarn of poorer quality, i.e. a yarn characterised by irregularities in the form of thick and thin zones, in relation to opening rollers of the type in which the base region of the sawtooth wire is embedded in a helical groove. An investigation into the cause of these irregularities has shown that the parallel position of the fibres separated by the opening roller is inadequate.